Manufacture of platinum-containing alumina catalyst



3,003,973 MANUFACTURE OF lLATlNUM-CBNTAINING ALUMINA CATALYST Robert M. Smith, Berwyn, llh, assignor, by rnesne assignments, to Universal Gil Products Company, Des Plaines, 11]., a corporation of Delaware No Drawing. Filed Jan. 19, 1959, Ser. No. 787,326 8 tllaims. (Cl. 252441) The present application is a continuation-in-part of my ,c'o-pending application, Serial Number 581,281, filed April 30, 1956, now abandoned, and relates, in its broad scope, to the manufacture of platinum-containing catalyst. More specifically, the present invention is directed to an improvement in processes for manufacturing platinumcontaining catalyst, in which processes the platinum is composited with a refractory inorganic oxide in the presence of ammonium hydroxide and an oxidizing agent. Those oxidizing agents most widely employed, and to which the instant invention is particularly applicable, are selected from the group consisting of hydrogen peroxide and ammonium nitrate.

As produced in accordance with the method of the present invention, the platinum-containing catalyst is especially adaptable to the conversion of hydrocarbons, and affords unexpected benefits to those processes for the catalytic reforming of lower-boiling petroleum fractions into motor-fuel fractions possessing unusually high antiknock characteristics. The term, reforming, is well known in the petroleum industry, and refers to the treatment of gasoline and naphtha fractions to improve their antiknock characteristics. Reforming has been effected on various petroleum fractions including full boiling range gasolines, straight-run and natural-gasolines, cracked gasolines, mixtures of various gasolines, as well as selected narrow boiling range fractions. The feed stock to a catalytic reforming unit will usually have an initial boiling point not less than about 75 F., and an end boiling point not greater than about 450 F.

In the reforming process, there are four principal reactions which are effected virtually simultaneously; the first is aromatization, in which naphthenic hydrocarbons are converted to aromatic hydrocarbons; the second is dehydrocyclization, in which aliphatic hydrocarbons, of a straight-chain or slightly branched-chain configuration, are cyclized and then dehydrogenated to form aromatic hydrocarbons; the third reaction is isomerization, in which straight-chain or slightly branched-chain aliphatic hydrocarbons are converted to a more branched molecular configuration; the final principal reaction is hydrocracking, in which the larger parafiinic molecules are cracked to form smaller paraffinic molecules. The com bined effect of these reactions results in the production of high-octane material from low-octane material, and therefore, all act to produce a more desirable motor fuel. The hydrocracking reaction must, of necessity, be somewhat limited so that it does not produce an excessive quantity of molecules which boil Within the normally gaseous boiling range; inherently, this results in severe liquid yield losses. To illustrate, if a normal decane molecule were cracked to produce two isopentane molecules, not only would a substantial octane increase be effected, but an actual liquid volume increase would be experienced. If, however, the cracking were uncontrolled, the normal decane would be cracked to form three propane molecules and one methane molecule; the final result is that the normal decane molecule is totally lost in regard to the liquid yield of desired product.

Although the particular catalyst, prepared by the method of the present invention, is most suitable for reforming, it may be used to promote other reactions including the hydrogenation and dehydrogenation of specific Patented Oct. 10, 1961 compounds or hydrocarbon fractions, isomerization of specific compounds or hydrocarbon fractions under particular operating conditions, destructive hydrogenation or hydro'crackiug of large molecules such as those boiling in the kerosene and gas-oil range or heavier, and oxidation of hydrocarbons such as the oxidation of normal butene to produce normal butyl alcohol. resulting from the utilization of the present invention may be used in treating processes, wherein small quantities of undesirable contaminants are removed, which treating processes include desulfurization of gasoline fractions whereby sulfur-bearing hydrocarbon molecules are treated to form hydrogen sulfide and the corresponding saturated hydrocarbon.

Until recently, the use of platinum as a catalytic agent had not been commercially feasible due to the initial high cost of the platinum metal. 7 Recent developments, however, have resulted in catalysts having suflicient activity to effect reactions such as those hereinbefore described, and which contain as little as 1.0% or less by weight of platinum. When such small quantities of platinum are utilized, it is necessary that the platinum be employed in a form which will yield the greatest advantage. Since catalysis is known to be a surface phenomenon, it is desirable that the small quantity of platinum be thoroughly and uniformly distributed in order to produce the greatest surface area per unit of volume. It is also desirable that the platinum be employed in a state such that its catalytic activity is the greatest. It has been found that when platinum is placed in distended condition on an alumina support, a peculiar association exists between the platinum and alumina which produces a composite having high activity. Further, high catalytic activity demands that the platinum exist in a form such that it is readily oxidized to the highest valence state. A small quantity of halogen, selected from the group consisting of chlorine, fluorine and mixtures thereof, is generally composited with the refractory oxide and platinum in a loose chemical or physical association, and has been found to enhance the selectivity of the final catalytic composite in promoting the various reforming reactions. The method by which the various catalytic components are composited with the'carrier material is critically important in determining the ultimate association of the components one to the other. Finally, as hereinafter set forth, it is essential to high catalytic activity that the platinum, when composited with the carrier material, and the other catalytic components, is not permitted to form an ammonium complex.

The object of the present invention is to provide a means of compositing the catalytic components with the refractory inorganic oxide, or more specifically, platinum and combined halogen composited with alumina, such that each individual component, and the combination of components, exists in a state most advantageous to a high degree of catalytic activity.

The usual method of compositing platinum with a re fractory inorganic oxide, such as alumina, is to immerse particles of alumina in a solution of a soluble platinum compound, thereafter separating the particles from the solution, and drying and calcining the same. The particles of alumina may be powder, powder pressed into the form of cylinders or pellets, or spherical alumina manufactured by, well-known methods from alumina hydrosols. As far as the method of the present invention is concerned, all of these forms of alumina, or other refractory material, are substantially equivalent. The invention will be described, therefore, in relation to cylindrical pellets for the sake of simplicity and clarity, and with no intention of limiting the invention to this particular form.

It has been found that when a soluble platinum com- The catalyst pound, in solution, is impregnated within cylindrical pellets of alumina, and the alumina pellets are separated from the liquid, treated with hydrogen sulfide to convert the platinum to the form of platinum sulfide and subsequently dried and calcined, the platinum is disposed around the outer surfaces of the pill and very little penetrates to the innermost surfaces. A pellet prepared in this manner, when split in two and examined, shows a dark outer rim with an abrupt line between it and a substantially White center. This color gradient indicates that most of the platinum, in the form of platinum sulfide, is at the outer edge of the pellet and, therefore, the platinum molecules present therein are crowded into a relatively small volume, and are not sufiiciently thoroughly distributed for optimum catalysis. It is well-known that to avoid this difiiculty, ammonium hydroxide may be mixed with the impregnating solution, which is preferably a water solution of chloroplatinic acid. The use of ammonium hydroxide in some manner causes the platinum to become uniformly distributed throughout the pellet of alumina, and a dried and calcined pellet prepared in this manner, when out in half, exhibits a uniform gray color throughout its entire cross section. Pellets prepared in this manner, however, do not exhibit the activity that would be expected, and it is theorized, but not definitely determined, that this is due to the fact that the presence of ammonia causes the platinum to form an ammonium complex, or exist in a reduced state, and, therefore, such platinum does not associate with the alumina in a form which is readily oxidized to the highest valence state. It is an object of this invention to overcome this detrimental effect of ammonia, and thereby produce a catalyst pellet in which the platinum is both uniformly distributed and associated with the alumina in such a way as to promote catalytic activity to an unusually high degree.

This object is accomplished by impregnating aluminacontaining material with an impregnating solution containing a soluble form of platinum, ammonium hydroxide, an oxidizing agent which is effective at low temperatures, that is, below about 212 F., and an oxidizing agent eifective at high temperatures, or above about 212 F. As hereinbefore stated, the platinum containing solution may comprise any soluble form of platinum such as chloroplatinic acid, bromoplatinic acid, fiuoroplatinic acid, etc. The ammonium hydroxide may be emplayed in any suitable strength or it may be formed in situ by bubbling ammonium gas through the impregnating solution. The oxidizing agent, effective at temperatures below 212 F. is preferably hydrogen peroxide since its decomposition products are water and oxygen which introduce no residueforming material into the mixture. The preferred high temperature oxidizing agent is ammonium nitrate. This material is also preferred due to the fact that it can perform its function while employing only volatile components, and may be removed from the composite very readily. Other oxidizing agents such as aluminum nitrate, nitric acid, etc. may be used. The quantity of oxidizing agents employed is not critical and may vary over a wide range. Enough of each should be used to be effective, cg. about by weight of the platinum, but not so much as to be over-abundant, e.g. less than about 3000% by weight of platinum or more. However, since addi tional amounts are neither effective nor harmful, the upper limit is not important.

In one embodiment, the present invention relates to an improvement in processes for the manufacture of platinum-containing, alumina catalyst, wherein alumina is impregnated with a water-soluble platinum compound in the presence of ammonium hydroxide and an oxidizing agent selected from the group consisting of hydrogen peroxide and ammonium nitrate, the improvement which comprises commingling alumina, a water soluble platinum compound and hydrogen peroxide with ammonium hydroxide at a temperature below 212 F., heating the resuiting mixture to a temperature in excess of 212 F., adding ammonium nitrate thereto when said temperature attains 212 F., drying the resulting mixture and thereafter calcining the dried mixture.

In another embodiment, the present invention provides an improvement in processes for the manufacture of platinum-containing, alumina catalyst, wherein alumina is impregnated with a water-soluble platinum compound in the presence of ammonium hydroxide and an oxidizing agent selected from the group consisting of hydrogen peroxide and ammonium nitrate, the improvement which comprises commingling alumina containing from about .l% to about 8.0% by weight of combined halogen, chloroplatinic acid in an amount sufiicient to yield a final catalyst containing from about 0.01% to about 1.0% by weight of platinum, and hydrogen peroxide with ammonium hydroxide at a temperature below 212 F., heating the resulting mixture to a temperature in excess of 212 F., adding ammonium nitrate thereto when said temperature attains 212 F., drying the resulting mixture and thereafter calcining said mixture at a temperature within the range of from about 500 F. to about 1100 F.

In its most specific embodiment, the present invention aflords an improvement in processes for the manufacture of a platinum-containing, alumina-combined halogen catalyst, wherein alumina is impregnated with a Watersoluble platinum compound in the presence of ammonium hydroxide and an oxidizing agent selected from the group consisting of hydrogen peroxide and ammonium nitrate, which improvement comprises commingling alumina containing from about 0.1% to about 8.0% by weight of combined halogen, selected from the group of chloride and fluoride, with hydrogen peroxide, in the absence of ammonium nitrate and ammonium hydroxide, adding chloro-platinic acid thereto in an amount sufiicient to yield a final catalytic composite containing from about 0.01% to about 1.0% by weight of platinum, thereafter adding ammonium hydroxide at a temperature below about 212 F., heating the resulting mixture to a temperature in excess of 212 F., adding ammonium nitrate thereto when said temperature attains a level of 212 F., drying the resulting mixture and thereafter calcining said mixture at a temperature within the range of from about 500 F. to about 1100 F.

Although the particularly preferred carrier material comprises alumina, to which combined halogen has been added in an amount of 0.1% to about 8.0% by weight (calculated as elemental chlorine and/or fluorine), other refractory inorganic oxides may be utilized, in addition to, or instead of, the halogen, and include silica, zirconia, titania, boria, and mixtures thereof. The use of any given combination of refractory oxide-material is generally dependent upon the particular use of the catalyst, and the desired degree to which specified reactions are to be effected. It is understood that the use of any of the aforementioned refractory inorganic oxides is not limiting upon the broad scope of the present invention. The essential feature of the present invention, which results in the improvement over the prior art, lies in the particular method of utilizing the ingredients employed during the impregnation of the carrier material with the catalytically active metallic component, whereby the formation of an ammonium-platinum complex is prevented.

Briefly, the particularly preferred method of effecting the improved catalyst of the present invention comprises commingling alumina with an amount of an aqueous solution of chloroplatinic acid, sufiicient to result in a final catalytic composite containing from about 0.01% to about 1.0% by weight of platinum, and hydrogen peroxide in an amount of at least 10% by Weight of the platinum. The ammonium hydroxide is added to the resulting mixture only after the alumina is thoroughly saturated with the hydrogen peroxide, as Well as the chloroplatinic acid. That ammonium hydroxide not be caused to contact the alumina and chloroplatinic acid, is in the absence of the hydrogen peroxide, is to insure further against the formation of an ammonium-platinum complex. Similarly, the ammonium nitrate is not added until a temperature of 212 F. is reached, while drying the mixture, or until the ammonium nitrate becomes effective as an oxidizing agent rather than a source of ammonium ions.

Following the addition of the ammonium hydroxide to the mixture of alumina, chloroplatinic acid and hydrogen peroxide, the temperature is increased to a level of 212 F. This effects the initial phase of the drying of the mixture, and care must be taken to avoid a rapid temperature rise resulting in the sudden evolution of Water vapor and nther gaseous material. The ammonium nitrate is added to the mixture when the temperature of the same ,is 212 F., and additional heat applied to complete the drying of the composite. The dried composite is thereafter subjected to a calcination procedure, in an atmosphere of a suitable free oxygen-containing gaseous material, at a temperature within the range of about 500 F. to about 1100 F.

As hereinbefore stated, when the pellets have been impregnated with the solution, they are separated from the liquid, and thereafter dried and calcined. The calcination should be effected under oxidizing conditions, that is, in the presence of air, or other suitable free oxygen-containing gaseous material, since it has been found that oxidizing the platinum when it is newly deposited upon the alumina fixes it into its association with the alumina in such a manner that subsequent exposure to reducing conditions does not detrimentally affect the activity. In many cases, the calcined catalyst is reduced, for example in a stream of hydrogen, before introduction into a reforming zone. This reduction does not harm the catalyst and in fact increases its initial activity. However, as hereinbefore stated, an oxidizing calcination should be effected first, and the catalyst is always calcined after impregnation. The alumina support is preferably calcined before impregnation, however, this step may be eliminated and impregnation may be effected on a wet alumina gel.

The catalyst is most useful for effecting reforming reactions which were discussed previously. More specifically, reforming is effected at elevated pressure, from about 50 pounds per square inch to about 1000 pounds per square inch or more, and at elevated temperatures, from about 700 F. to about 1000 F. or more in the presence of hydrogen. Generally, the reforming is effected by passing a preheated hydrocarbon charge into the upper portion of a reaction zone containing a fixed bed of catalyst pellets, and circulating a hydrogen atmosphere therethrough while effecting the reactions. The efliuent flowing from the reaction zone is passed to a separation zone wherein the normally gaseous material is separated from the normally liquid material. The normally gaseous material, which is mainly hydrogen, usually in exce s of 80% by volume of the total gas, is returned in part to the reforming zone to provide the necessary hydrogen atmosphere, however, when the charge stock is extremely righ in naphthenic material, sufiicient hydrogen may be produced in the reaction zone to supply all that is required without recycle. Conversely, some charge stocks may be so naphthene deficient, or the reactions to be effected, for example olefin saturation or desulftuization, may be such that an extraneous source of hydrogen is required to provide a suflicient amount within the reaction zone.

The process may be effected in a fixed bed, moving bed, or fluidized bed of catalyst, and may incorporate periodic regeneration of the catalyst either by interrupting the flow of hydrocarbon, and contacting the catalyst with free oxygen, or by continuously moving the catalyst cyclically between a reaction zone and a regeneration zone. The latter method will be more easily accomplished when a moving catalyst process is being used, and the former method when a fixedbed process is employed. The presence of hydrogen in the reaction zone is necessary to cause saturation of cracked fragments and to prevent the excessive deposition of coke and other carbonaceous material on the catalyst thereby covering its active surface and destroying the activity. The use of sufficient hydrogen may eliminate the need for regeneration, but when required, the catalyst of this invention is readily adaptable to oxidative regeneration.

As hereinbefore set forth, the present invention effects an improvement in processes for the manufacture of platinum-containing catalytic composites through the cojoint utilization of two oxidizing agents. The essential feature of the present invention resides in the particular method in which these oxidizing agents are employed. That is to say, the catalyst-impregnation procedure is effected in two distinctly individual stages, in each of which a particular oxidizing agent is used. The need for an oxidizing agent to be present during the impregnation procedure arises as a result of the use of ammonium hydroxide, this being employed to insure uniform distribution of the platinum compound throughout the carrier material, but which in turn results in the formation of an ammonium-platinum complex. The function ofthe oxidizing agent is to prevent the formation of this complex to insure that the platinum, when the composite is dried and subsequently calcined, will exist in its most highest oxidized state, or in the highest possible valence state. Such a result cannot be obtained where the platinum-ammonium complex is formed. This is believed to be due to the stability of said complex when subjected to the elevated temperatures employed during the drying and calcining procedures. The oxidizing agents most widely employed, since they do not form detrimental residual material upon heating, are hydrogen peroxide and ammonium nitrate. I have found that a totally unexpected result is obtained through the cojoint use of these oxidizing agents in a particular manner, which result is not obtained through the us of either alone, or by employing a mixture thereof.

The drying and calcining procedures are generally effected throughout a temperature increase ranging from about room temperature (about F.), through the dry ing stage (up to about 250 F. to 300 F to the elevated temperature of the calcination procedure (about 1000 F.). I have found that hydrogen peroxide is effective in preventing the formation of the ammonium-platinum complex only below 212 F., and this regardless of any excessive quantity which might be employed. On the other hand, ammonium nitrate is extremely effective above a temperature of 212 F., and is inefliective at temperatures below 212 F. In fact, the use of ammonium nitrate as the oxidizing agent below a temperature of about 212 F. virtually destroys its intended function and obviates the purpose it is to serve. The ammonium nitrate does not act as an oxidizing agent below 212 F., but rather readily ionizes to supply additional ammonium ions to the impregnating mixture, increasing thereby the tendency to form the ammonium-platinum complex. This result is diametrically opposed to the successful attainment of the desired object.

Therefore, the method of the present invention involves the utilization of hydrogen peroxide at temperatures below 212 B, when the impregnation mixture is being subjected to the initial drying, and the use of ammonium nitrate when the temperature is increased beyond 212 F., to complete the drying and effect calcination of the catalytic composite. To employ the hydrogen peroxide and ammonium nitrate simultaneously, as a mixture, at temperatures below 212 F. would tend to inhibit the protection afforded through the use of the hydrogen peroxide alone.

The following example is given to illustrate the method 7 of the present invention, and to indicate more clearly the definite beneficial improvement derived through the utilization thereof. It is understood that the present invention is not limited unduly to the reagents, concentrations, conditions and procedure employed therein; the present invention is intended to be limited in scope by the spirit of the appended claims.

Example 130 grams of alumina spheres were impregnated with a solution containing 220 milliliters of water, 7.8 milliliters of chloroplatinic acid containing 0.0625 gram of platinum per milliliter of solution and 6.8 milliliters of an ammonium hydroxide solution containing 0.0215 gram of ammonia per milliliter of solution. The spheres were immersed in the solution for one-half hour, the mixture then being dried on a Water bath and thereafter calcined in air at 930 F. for a period of four hours. The resulting catalyst contained 0.375% by weight of platinum, and, for the purposes of this discussion, is designated as catalyst A.

A second batch of 130 grams of alumina spheres was commingled with 220 milliliters of water and 7.8 milliliters of the same chloroplatinic acid solution and 6.8 milliliters of the same ammonium hydroxide solution. This mixture was heated on a water bath to a temperature of 210 F. and 13 milliliters of a 10% ammonium nitrate solution was then added. The mixture was dried on the water bath, and calcined in air at 930 F. for four hours. This catalyst, which is designated as catalyst B, contained 0.375% by weight platinum.

A third batch of catalyst was prepared by impregnating 130 grams of alumina spheres with a solution containing 220 milliliters of water, 7.8 milliliters of the same chloroplatinic acid solution, and 4.9 grams of a 30% by weight hydrogen peroxide solution to which was added 6.8 milliliters of the same ammonium hydroxide solution previously used. The mixture of the alumina spheres and impregnating solution was dried on a water bath and calcined in air at 930 F. for four hours and this catalyst, which contained 0.375% by weight of platinum, is designated catalyst C.

A fourth batch of catalyst was prepared by impregnating 130 grams of alumina spheres with the same solution containing chloroplatinic acid, hydrogen peroxide and ammonium hydroxide as that used in the preparation of catalyst C." This mixture of alumina spheres and impregnating solution was heated 210 F. and then 13 milliliters of ammonium nitrate solution was added. The mixture was then dried on a water bath and calcined in air at 930 F. for four hours. This catalyst contained 0.375% by weight of platinum, and is designated catalyst (KD'QY The catalysts A, B, C and D were of the same ultimate composition. both as to components and the concentrations thereof. They were different only by their methods of preparation. Catalyst A was prepared with no oxidizing agent. Catalyst B was prepared with an oxidizing agent effective only at high temperatures. Catalyst C was prepared with an oxidizing agent effective only at low temperatures, and catalyst D was prepared by the method of this invention which employs two oxidizing agents, one effective at high temperature and one effective at low temperature.

Catalysts A, B, C and D were individually utilized in reforming a Gulf-Coast naphtha having a boiling range of from 260 F. to 398 F., and an F-l clear octane number of 3.0. The inlet temperature to the reactor was, in all cases, 950 F., a pressure of 500 pounds per square inch was imposed thereupon, a liquid hourly space velocity of 2.23 volumes of liquid per volume of catalyst per hour was used, and a hydrogen to hydrocarbon mol ratio of 11.0 was employed. The results of the reforming runs are given in the following table:

Excess Re- Dcbutauizcr Ratio of De- Oatalyst Designation ceivcr Gas Gas (s.c.t./ butanizcr to (s.c.t./bb1.) bbl.) Receiver Gas As may be readily ascertained from an inspection of the above table, the use of an oxidizing agent in the impregnating solution caused an improvement in the catalyst over an impregnation without an oxidizing agent. However, unexpectedly, the combined use of two oxidizing agents, in accordance with the present invention, resulted in as great an improvement over the catalyst impregnation employing one oxidizing agent as the improvement resulting through the use of a single oxidizing agent. The improvement is reflected in the ratio of debutanizer gas make to receiver gas make. The significance of these numbers is as follows: the receiver gas make is a measure of how much hydrogen is produced by the process over that required for it to sustain itself. The etlluent from the reaction zone, as hereinbefore described, passes to a separation zone in which the liquid product is separated from the normally gaseous material. Whatever normally gaseous material is required to maintain sufficient hydrogen atmosphere in the reaction zone is taken and passed to the reaction zone, and the excess is removed from the process; this excess gaseous material is the receiver gas of the table. The normally liquid material from the first separation passes to a debutanizer which, as the name indicates, removes hydrocarbon material including butane and lower boiling hydrocarbons. The volume of debutanizer gas produced indicates both the selectivity and the extent of hydrocracking. The ratio of these two figures is a measure of the efficiency of the catalyst in producing an octanenumber increase in the desired manner, that is, by dehydrogenation of naphthenes and selective hydrocracking rather than by random hydrocracking with its resultant loss of liquid yield. In all cases illustrated above, the F-1 clear octane number of the product was between 89 and 91.5.

The foregoing example illustrates conclusively that the method of this invention provides a means of obtaining an improved catalyst by altering only the method of manufacture. The data indicates that the catalyst manufactured from impregnating solutions containing particular oxidizing agents at particular temperatures, produces a result which cannot be achieved with the use of either of the oxidizing agents alone. This has been accomplished through the elimination of the ditficulties arising as the result of the formation of the ammonium-platinum complex. The present invention recognizes the need for ammonium hydroxide in an impregnating solution, and yet overcomes the difficulty associated with its utilization. The present invention also recognizes the need for an oxidizing agent, and, furthermore, indicates the advantages alforded by having an effective oxidizing agent pres ent in all stages of the catalyst preparation. This method provides a catalyst in which the catalytically active metal is uniformly distributed throughout the composite, and possesses a high degree of catalytic activity.

I claim as my invention:

1. In a process for the manufacture of platinumcontaining, alumina catalyst, wherein alumina is impregnated with a water-soluble platinum compound in the presence of ammonium hydroxide and an oxidizing agent selected from the group consisting of hydrogen peroxide and ammonium nitrate, resulting in the formation of an ammonium-platinum complex, the improvement which comprises commingling alumina, a water-soluble platinum compound and hydrogen peroxide with ammonium hydroxide at a temperature below 212 F., heating the I 9 resulting mixture to a temperature in excess of 212 F., adding ammonium nitrate thereto when said temperature attains 212 F., drying the resulting mixture and there after calcining said mixture.

2. The process of claim 1 further characterized in that said platinum compound comprises chloroplatinic acid.

3. The process of claim 1 further characterized in that said alumina contains combined halogen.

4. The process of claim 2 further characterized in that said chloroplatinic acid is employed in an amount suflicient to yield a final composite containing from about 0.01% to about 1% by weight of platinum.

5. In a process for the manufacture of platinumcontaining, alumina catalyst, wherein alumina is impregnated with a water-soluble platinum compound in the presence of ammonium hydroxide and an oxidizing agent selected from the group consisting of hydrogen peroxide and ammonium nitrate, resulting in the formation of an ammonium-platinum complex, the improvement which comprises commingling alumina containing from about .1% to about 8.0% by weight of combined halogen,

chloroplatinic acid in an amount suflicient to yield a final catalyst containing from about 0.01% to about 1.0% by weight of platinum, and hydrogen peroxide with ammonium hydroxide at a temperature below 212 F., heating the resulting mixture to a temperature in excess of 212 F., adding ammonium nitrate thereto when said temperature attains 212 F., drying the resulting mixture and thereafter calcining said mixture at a temperature within the range of from about 500 F. to about 1100 F.

6. The process of claim 5 further characterized in that said combined halogen comprises combined chloride.

7. The process of claim 5 further characterized in that said combined halogen comprises combined fluoride.

8. The process of claim 5 further characterized in that the commingling of said alumina, chloroplatinic acid, hydrogen peroxide and ammonium hydroxide is efiected in the absence of ammonium nitrate.

References Cited in the file of this patent UNITED STATES PATENTS 2,781,324 Haensel Feb. 12, 1957 

1. IN A PROCESS FOR THE MANUFACTURE OF PLATINUMCONTAINING, ALUMINA CATALYST, WHEREIN ALUMINA IS IMPREGNATED WITH A WATER-SOLUBLE PLATINUM COMPOUND IN THE PRESENCE OF AMMONIUM HYDROXIDE AND AN OXIDIZING AGENT SELECTED FROM THE GROUP CONSISTING OF HYDROGEN PEROXIDE AND AMMONIUM NITRATE, RESULTING IN THE FORMATION OF AN AMMONIUM-PLATINUM COMPLEX, THE IMPROVEMENT WHICH COMPRISES COMMINGLING ALUMINA, A WATER-SOLUBLE PLATINUM COMPOUND AND HYDROGEN PEROXIDE WITH AMMONIUM HYDROXIDE AT A TEMPERATURE BELOW 212*F., HEATING THE RESULTING MIXTURE TO A TEMPERATURE IN EXCESS OF 212*F., ADDING AMMONIUM NITRATE THERETO WHEN SAID TEMPERATURE ATTAINS 212*F., DRYING THE RESULTING MIXTURE AND THEREAFTER CALCINING SAID MIXTURE. 